How to clean a spark plug ? [ carbon coated ]

You will never clean them where they will work efficiently again. That carbon seats between the wedge in the porcelain and the steel and shorts the plug. We race 2 strokes for many years. Once a plug is shorted with oil and carbon they are junk. Cleaning them will get you a lap or 2 or to the store to get a new set. And the plug cleaner? We have one and it ruined more plugs then it saved. Media wedged in the plug is worse then oil and carbon.